Correlation of the Native Inaba Strain With the Dominant Isolated Strains Obtained From Outbreaks in 2013 in Iran

Background: Cholera is an endemic disease in Iran and each year we are faced with some outbreaks throughout the country. Objectives: The objective of this study was to analyze the isolated cholera strains from outbreak in 2013 and study their similarity and compare their homology in order to find out the route of infection whether emerged from foreign strains or reemerged from domestic native strains. Materials and Methods: All diagnosed Vibrio cholerae isolates were entered to the study after re-identification at referral laboratory of Ministry of Health and Medical Education based on standard procedures. These specimens were examined for specific serogroups by O1 polyvalent and Ogawa/Inaba monospecific antisera and tested by MIC Test Strip Method against ciprofloxacin (CIP), nalidixic acid (NA), cefixime (CFM), ampicillin (AMP), tetracycline (TE), trimethoprim-sulfamethaxazone (SXT), and erythromycin. Results: A total of 257 clinical V. cholerae was isolated from 2013 outbreak in Iran. The dominant causative type was Inaba. Vibrio cholerae was reported and isolated from 12 provinces, while 81.71% of cases was from two southeast provinces. The outbreaks started from August and lasted till November. According to antibiotic susceptibility test, isolates were 100% resistant to NA, TE, and SXT, while all were sensitive to CIP, CFM, and AMP. Twenty-three percent of strains were sensitive to erythromycin and all were isolated at the first two weeks of outbreak either from Iranian citizens or from foreign travelers. Homology of isolates was investigated through genotyping by pulse field gel electrophoresis (PFGE) method and their clonality was compared with previously-isolated Iranian native strains. Overall, 92% of analyzed strains showed a homolog pattern. These strains were located in 8 clusters. Although isolated strains in 2011 had 80% homology to recent isolates, they were located in a totally distinct cluster from all strains isolated in 2013. PFGE analysis revealed no dissimilarity between resistant and sensitive stains to erythromycin. Conclusion: This study confirmed that isolated Inaba strains in 2013 had different clonality patterns in PFGE from previously identified strains, suggesting the presence of a foreign route, namely, from the neighboring countries.